A magnetic disk device includes a P list (primary list) in which a sector (hereinafter, referred to as a defective sector) containing a defect, such as a scratch detected in an inspection before shipment, is registered and a G list (grown list) in which the defective sector detected after shipment is registered. Usually, the sector containing a minor defect, such as a thin scratch that could be written and read without any problem before shipment, may not be registered in the P List. The sector including such a minor defect may be located in the vicinity of the defective sector, or the like, and registered in the P list. For that reason, when a defective sector is detected in the vicinity of the defective sector registered in the P list after shipment, a sector located in the vicinity of the defective sector registered in the P list and the defective sector detected after shipment may become a defective sector due to age-related deterioration, growth of scratches of the defective sectors registered in the surrounding P list or G list, and the like.